Generally, as a brake disk of a disk brake system for a motorcycle, there has been widely put to practical use a so-called floating brake disk which is provided with an annular braking disk against which a brake pad is to be pressed, a hub disk to be attached to the inside of the braking disk, and a plurality of connecting means for connecting both of the disks to each other in a floating state and configured to be able to prevent the brake disk from being deformed and warped in whole due to heat generation when a brake is operated by utilizing a space between both of the disks.
As for the connecting means, there has been widely used connecting means which is configured in such a manner that a plurality of braking side connecting concave portions is formed in an inner circumferential portion of the braking disk, a plurality of hub side connecting concave portions opposed to the braking side connecting concave portions is formed in an outer circumferential portion of the hub disk, connecting pins are respectively mounted in connecting holes each of which is formed by combining each of the braking side connecting concave portions with the respective hub side connecting concave portions, a disk spring and a washer are attached to the outside of the connecting pin, and an end portion of the connecting pin is swaged so as to connect both of the disks in a floating state through the disk spring (see Patent Document 1, for example).
As for the connecting pin, there has been used a connecting pin which is provided with a substantially cylindrical body portion to be mounted in a connecting hole with substantially no space therebetween, a first flange portion formed in one end portion of the body portion and having a diameter larger than that of the connecting hole, a to-be-swaged portion formed in the other end portion of the body portion and having a diameter smaller than that of the body portion, and a stepped portion formed in a boundary between the body portion and the to-be-swaged portion, and configured such that the body portion is mounted in the connecting hole in a state that a disk spring is attached to the body portion and the to-be-swaged portion is then swaged in this state to form a second flange portion, so that the disk spring and the connecting pin are fixed to both of the disks through the second flange portion to thereby connect both of the disks in a floating state, as described in Patent Document 1.
In the meantime, as for a method for swaging the to-be-swaged portion of the connecting pin, there are known a method in which an insert is inserted into the to-be-swaged portion and then rotated so as to gradually extend the diameter of the to-be-swaged portion to thereby swage the to-be-swaged portion as described in Patent Document 1 and a method in which the to-be-swaged portion is pressed by a punch having a molded portion which is fitted into the second flange portion to thereby swage the to-be-swaged portion as described in Patent Document 2.